The present invention relates to a plasma treatment apparatus and a plasma treatment method for etching and cleaning the surface of a workpiece (hereafter called a work).
In the electric industry, a plasma treatment is known for etching the surface of a semiconductor wafer (hereafter called a wafer) and cleaning the surface of a printed circuit board. The plasma treatment apparatus holds the work such as a wafer, the printed board or the like between two electrodes in a vacuum chamber, and generates plasma by applying a high-frequency voltage between these electrodes and performs the plasma treatment by bombarding ions, which are generated between two electrodes, against the surface of the work.
Deep etching (for example 5 xcexcm) over the wafer is needed to thin the wafer or to remove a stress layer (a layer having cracks by machine grinding) in the polished surface of the wafer. However, in the conventional plasma treatment apparatus, if plasma density is low and also the etching rate (an etching speed) is low, it takes much time to perform deep-etching, therefore, the conventional plasma treatment is difficult or is practically impossible to use in these circumstances from an economical aspect.
In a conventional plasma treatment apparatus, it is preferable to increase plasma density by narrowing the spacing between two electrodes to provide a high etching rate.
However, a holding head holds the work to be plasma treated, such as the wafer or printed circuit board, and transfers to and from a space between the electrodes. When the spacing narrows by closing the spacing between the electrodes, it is difficult or impossible to transfer the work to and from the space between the electrodes with the holding head.
Moreover, in the conventional plasma treatment apparatus, the work is fixed on a lower electrode by a static chuck. As the static chuck is quite expensive, and it results in a high cost.
The purpose of the present invention is to provide a plasma treatment apparatus with increased etching rate by closing a spacing between two electrodes during a plasma treatment and to provide an inexpensive plasma treatment apparatus which can transfer the work to and from the apparatus easily, thereby solving the foregoing problems.
A plasma treatment apparatus in the present invention comprises:
(1) a vacuum chamber;
(2) an upper electrode and a lower electrode;
(3) a high-frequency power supply applying a high-frequency voltage to the upper and lower electrode;
(4) a space adjusting means for adjusting a spacing between the upper electrode and the lower electrode; and
(5) a work-transfer means for transferring the work to and from the space between the upper electrode and the lower electrode.
According to the configuration of the present invention, the upper electrode and the lower electrode are kept closed to each other during a plasma treatment and an etching rate can be increased, therefore, a plasma treatment becomes faster. Moreover, when transferring the work to and from the space between the electrodes, the space between the upper electrode and the lower electrode is opened, and the work can be transferred to and from the space with ease.